1. Field of the Invention
The present invention relates to a cold cathode ionization vacuum gauge, a vacuum processing apparatus using the same, and an auxiliary discharge starting electrode plate, and particularly relates to an inverted magnetron cold cathode ionization vacuum gauge.
2. Description of the Related Art
A cold cathode ionization vacuum gauge measures a gas pressure by initiating ionization of the gas through self discharge of an anode and a cathode. Cold cathode ionization vacuum gauges of a penning type, a magnetron type, and an inverted magnetron type have been known as conventional cold cathode ionization vacuum gauges (see Japanese Patent Application Publication No. Hei 10-19711). In particular, the magnetron type and inverted magnetron type are suitable for high vacuum measurement because of their high electron trapping efficiencies as well as structures which allow stable sustained discharge even in a high vacuum area.
Meanwhile, to start discharge in a cold cathode ionization vacuum gauge, it is necessary to initiate ionization through high voltage application. There is, however, a time delay between when a high voltage is applied to the cold cathode ionization vacuum gauge and when a discharge current begins to flow upon start of sustained discharge. This time delay affects the time until the start of the measurement.
In this respect, Japanese Patent Application Publication No. Hei 06-26967 discloses an inverted magnetron type cold cathode ionization vacuum gauge aiming to shorten the discharge initiation time from application of a high voltage to start of sustained discharge. The inverted magnetron type cold cathode ionization vacuum gauge in Japanese Patent Application Publication No. Hei 06-26967 is one in which a cathode is provided with discharge initiating means for directly emitting electromagnetic radiation large enough to release photoelectrons from the cathode.
In addition, Japanese Patent Application Publication No. 2008-304360 aims to provide an auxiliary ignition device which allows an improvement in assemblability of the auxiliary ignition device to a vacuum gauge body. Specifically, disclosed is a cold cathode ionization vacuum gauge including: a base part having a through-hole which is formed therein and through which an electrode penetrates; and an auxiliary ignition member including a protruding portion which projects from an inner peripheral surface of the through-hole toward the electrode.
Meanwhile, the conventional cold cathode ionization vacuum gauge described in Japanese Patent Application Publication No. Hei 06-26967 leads to complexity of the apparatus because the gauge is provided separately with means, such as a glow lamp or a UV exposure lamp, as means for initiating discharge, and a circuit for such means. Additionally, since the cold cathode ionization vacuum gauge of magnetron or inverted magnetron type exhibits a high trapping effect of charged particles, a wall surface of a chamber of the vacuum gauge is likely to be sputtered. The inside of the chamber of the vacuum gauge is therefore contaminated in some cases.
Thus, long term use of the vacuum gauge leads to adhesion of a sputtered film and/or a product onto a lamp surface, which in turn hinders emission of ultraviolet light. This, as a result, reduces the amount of photoelectrons to be generated which trigger discharge, and thus causes a problem of making discharge initiation difficult.
Meanwhile, in a case of using a cold cathode ionization vacuum gauge having an auxiliary ignition device as in Japanese Patent Application Publication No. 2008-304360, a dark current sometimes flows, and/or fluctuations sometimes occur in a discharge current after discharge is started.